From DE 39 34 733 A1, the expert is acquainted with a remote-control switch mechanism for a multistage change-over gear, in which a hand operated lever is connected over a change-over shifter rod with a gear-shifting shaft. This operative connection is chosen in such a way that a selective motion of the hand operated lever leads to an axial movement of the gearshift lever shaft and a switch motion produces the rotation of the gearshift lever shaft around its longitudinal axis.
A shift finger is formed on this gearshift lever shaft, which alternatively can mesh with the recess of shift rails and displace them axially. These shift rails on their part stand in operative connection with synchronization and coupling devices on wheel set shafts of the change-over gear in such a way, that in the execution of concrete processes of gear ratio modification, gearless wheels decelerate and can be connected in a torque proof manner to the gear shaft which carries them.
In such a combination of change-over gear and gear shift device, it is expedient in the realization of a short overall length of the gearing unit and low production costs, to arrange a synchronization and coupling device respectively between two lot gear wheels, which belong to two gears in the switching lane of an H-switching mechanism.
In this way, narrow limitations are imposed on the gearing unit construction, as well as the construction of the gear switching mechanism. Especially with a gearing unit with two lot wheels supported next to each other on a wheel set shaft, which do not belong to two gears that are arranged in a switching lane of an H-switching mechanism, a mechanical conversion mechanism is necessary, which, for instance with a switch motion of the gear shifting lever from first to second gear produces a shift out of gear of the synchronization and coupling device for first gear as well as a shift into gear of another synchronization and coupling device for second gear.
Based on this background, DE 102 31 547 A1 is known as a switching mechanism for a change-over gear, in which at least one of its switch sets is assigned to two gear ratio levels of the gearing unit which do not follow one another. Moreover, this switching mechanism is equipped with a mechanical conversion device, by means of which a hand-operated switching mechanism with an H-gear shifting gate can switch such a gearing unit.
With this switching mechanism, the gear shifting lever is directed into the H-gear shifting gate and coupled with two gearshift lever shafts, so that a movement of the switching lever into a switching lane leads to a swiveling of the first gearshift lever shaft along its longitudinal axis. In addition, a first gear wheel is attached to the first gearshift lever shaft, which meshes with a second gear wheel on the second gearshift lever shaft. With a rotation of the first gearshift lever shaft, the second gearshift lever shaft therefore counter rotates in the other direction. For the selection of a switching lane through the gear shifting lever, both gear shifting lever shafts are displaced in a forced coupling parallel to their longitudinal axis.
In addition, these two gearshift lever shafts possess shift fingers, which, depending on the gear shifted into, mesh with individually geared recesses of shifter rods, which are connected with shift claws. These shift claws on their part are connected with the shift sleeves of the shift sets, which in a switch operation are displaced to the torque proof connection of lot wheels with a gear shaft axially onto the respective gear shafts. p In addition, DE 102 53 471 A1, which is not published, describes a single rod gearshift for randomly settable gear positions of a change-over gear, in which a shifter lever and selector lever on the driver's side is coupled with an axially displaceable shift finger shaft, which can swivel around its longitudinal axis. This shift finger shaft, at every gear speed, possesses shift fingers for shifting into and out of gears, which mesh with the notches of respectively two switch housings assigned to gears.
For the selection of a gear, the shift finger shaft is axially displaced and for shifting into a gear is rotated around its longitudinal axis, so that in relation to the gear, respectively one shift finger meshes with one notch of the selected switch housing and displaces this essentially vertically to the longitudinal axis of the shift finger shaft. Shifter rods connected with the switch housings bear respectively upon shift claws, with which shift sleeves are axially displaceable upon them to a torque proof connection of gearless cog wheels with their wheel set shaft.
In addition, stop cams which can hinder an unallowable entrance of shift fingers into the respective shift housing, and which point radially to the shift finger shaft are formed on the shift housing.
Although these shifting mechanisms are connected with the advantage that, for instance, with the described gear and switch set arrangement, the gearing unit structure of a double coupling gearing unit is, with retention of almost all its components, also usable as a hand operated gearing unit as well as being switchable with an H-gear shifting gate, nevertheless the structure of these switching mechanisms is mechanically comparatively complex.
Upon this background, the task is, therefore, to introduce to the invention a switching mechanism for change-over gears, which features a mechanically more simple construction, whose operation can be more easily made automatic, and which is usable for double coupling gearing units as well as for change-over gears with only one low gear and switch coupling.